Magneto-dynamo-operated ingition device for multi-cylinder engines

ABSTRACT

A magneto-dynamic-operated ignition device for a multi-cylinder engine comprising a magneto dynamo, a plurality of discharge capacitors and a plurality of ignition coils; said magneto dynamo having a 2-pole rotor, an even-pole stator and an armature coil wound on every other pole of said stator poles, the number of which is determined depending on the number of cylinders; said discharge capacitors and ignition coils being equal in number to or half as many as the cylinders. Discharging circuits of the discharge capacitors are interrupted by a common rectifier which is controlled by ignition timing signals from ignition timing magneto dynamos.

[ 51 Mar. 27, 1973 1 MAGNETO-DYNAMO-OPERATED IGNITION DEVICE FOR MULTI-CYLINDER ENGINES [75] Inventor:

[73] Assignee: NippondensoC0.,Ltd.,Kariya-shi- Aichi-ken, Japan [22]Filed: Mar. 30, 1971 [21] Appl. No.: 129,342

Minoru Fujii, Kariya, Japan [30] Foreign Application Priority Data [58]Field of Search ..315/209 CD, 209 SC, 209 R, 315/211; 123/148 E, 148 DK,148 F, 148 ND, 149 A, 149 D [5 6] References Cited UNITED STATES PATENTS3,576,183 4/1971 Miyamoto ..l23/148 E Gilbert ..123/l48 E X Gibbs et al...315/209 CD Primary ExaminerRoy Lake Assistant Examiner-Lawrence J.Dahl Attorney-Cushman, Darby & Cushman [57] ABSTRACT Amagneto-dynamic-operated ignition device for a multi-cylinder enginecomprising a magneto dynamo, a plurality of discharge capacitors and aplurality of ignition coils; said magneto dynamo having a 2-pole rotor,an even-pole stator and an armature coil wound on every other pole ofsaid stator poles, the number of which is determined depending on thenumber of cylinders; said discharge capacitors and ignition coils beingequal in number to or half as many as the cylinders. Dischargingcircuits of the discharge capacitors are interrupted by a commonrectifier which is controlled by ignition timing signals from ignitiontiming magneto dynamos.

7 Claims, 10 Drawing Figures Patented March 27, 1973 2 Sheets-Sheet 1INVENTOR MIAIoEI-L FuJu MAGNETO-DYNAMO-OPERATED IGNITION DEVICEFOR-MULTI-CYLINDER ENGINES BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to a capacitor-discharge ignitiondevice mounted on an engine of an automotive vehicle.

2. Description of the Prior Art Hitherto, a capacitor-discharge ignitiondevice for multi-cylinder engines has been arranged that such eachcylinder is independently provided with an ignition coil, a controlledrectifier connected in series with the ignition coil and the gate of thecontrolled rectifier is applied with a trigger signal derived from anignition timing dynamo exclusive to the controlled rectifier. Such anarrangement, however, has a disadvantage in that the controlledrectifier for one of the cylinders is apt to be wrongly operated by asignal derived from one of the ignition timing dynamos belonging to anyother cylinder. Moreover, as a plurality of armature coils of themagneto dynamo are connected in series for producing a high ignitionvoltage to charge a discharge capacitor which is served to all thecylinders, it is necessary for the magnet dynamo to have a capability towithstand a high voltage and to be provided with a plurality ofpermanent magnet poles, which inevitably results in an uneconomicalproduction cost and a high temperature rise of the armature coils inoperation.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide a magneto-dynamo-operated ignition device for amulti-cylinder engine, in which a magneto dynamo is employed as a powersupply for charging a discharge capacitor and an high ignition voltageis produced at the secondary of ignition coils by discharging thecapacitor; the ignition device comprising a magneto dynamo having a2-pole rotor and a stator with poles of the even number which aredetermined according to the number of cylinders and with armature coilswound on every other pole thereof, and discharge capacitors and ignitioncoils respectively as many as or half as many as the cylinders;discharging circuits of the discharge capacitors being energized orcutoff by a common rectifier which is controlled by ignition timingsignals from the ignition timing dynamos.

By applying the device of this invention to a 2-cycle 3-cylinder engine,the capacitor voltage is made stable and erroneous energization of anunwanted ignition coil by the energization of a given ignition coil andreverse rotation of the 2-cycle engine are completely eliminated.Further, although two more capacitors and three more diodes are usedthan in the conventional device, rotor magnets are reduced to one third,the reverse breakdown voltage of the diodes to about one half, expensiveSCRs to one, capacitors for preventing erroneous energization to zero,and ignition timing dynamos to one. As a result of the saving of thevarious components, the circuit is simplified, thereby achievingconsiderable economy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an electric circuit ofthe conventional ignition device.

. tion.

FIG. 6a is an electrical circuit diagram showing the device according toanother embodiment of the invention.

FIG. 6b is a-diagram for explaining an example of the wider applicationof this invention.

FIGS. 7 to 9 are diagrams for explaining the operations of the deviceaccording to this invention, in which FIG. 7 is a diagram showingvariations of the magnetic flux inside the armature coils, FIG. 8showing waveforms of voltages produced in the armature coils and FIG. 9showing positions of the ignition timing dynamos for the generation ofignition timing signals.

A well-known conventional capacitor-discharge ignition device of thiskind employs a magneto dynamo shown in FIG. 2 as a power supply and itselectrical circuit is constructed as shown in FIG. 1. Such a device willbe described below with reference to FIGS. 1 and 2, taking as an examplea 2-cycle 3-cylinder engine with which the device is used.

An AC voltage generated by a magneto dynamo l is rectified by a diode 2and stored in a discharge capacitor 3. Charges stored in the capacitor 3are released through parallel-circuits respectively including ignitioncoils 5a, 5b and 5c and rectifiers 4a, 4b and 4c (hereinafter referredto as SCRs) with control electrodes which are energized through diodes11a, 11b

. and 110 by ignition timing signals supplied from ignition timingdynamos 10a, 10b and 100. The ignition timing signals are supplied bythe timing dynamos sequentially to the gates of the three SCRs' once forevery rotation of the crank shaft of the engine, thereby generatingignition sparks from ignition plugs 6a, 6b and 6c through ignition coils5a, 5b and 5c. Capacitors 7a, 7b, 7c, 8a, 8b and 8c are inserted toprevent any er- 'roneous energization of a rectifier with the controlelectrodes for a'cylinder which might be caused by an interferencesignal generated while another cylinder is in operation, therebylimiting the energizing signals to those from the timing dynamos.

The construction of the magneto dynamo 1 used in the above-describedcircuit is illustrated in FIG. 2. Since a 2-cycle 3-cylinder enginerequires three ignitions for every rotation of the crank shaft, a rotor17 which is driven by the crank shaft comprises a 6-pole magnet 12 andmagnetic-pole cores 13 arranged on its salient poles. The stator 14,like the rotor 17, has 6 salient poles on which are respectively woundarmature coils 15a, 15b, 15c, 15d, 15e and 15f connected in-se ries witheach other.

In the capacitor-charging magnet dynamo with the above-described circuitarrangement and construction, the reverse voltage E applied to the diode2 is the sum of the non-load voltage of the magneto dynamo 1 andcapacitor voltage E and is so high as to make it necessary to raise thebreakdown voltages of the parts involved. In addition, more heat isgenerated by the armature coils due to the 6-pole magnet 12 and due toan iron loss in the stator 14. Again, the voltage characteristic ofthe-capacitor assumes a dotted curve of FIG. 3, from which it isunderstood that the voltage is low at a low dynamo speed and increasesto a higher level with an increase in the speed of the dynamo, resultingin a great range of variation in the capacitor voltage. This presentsthe problem of providing a special voltageprotective circuit forobtaining stable capacitor charging voltages over the whole speed rangeif this device is to be employed for use with an automotive engine whichcovers a wide range of speeds. Further, the most serious problem is thefact that the rectifiers are often energized erroneously in spite of theprovision of the preventive capacitors 7a, 7b, 7c, 8a, 8b and 8c.

The construction of a magneto dynamo according to this invention isillustrated in FIG. 4, while an electric circuit of the device accordingto the invention employing such a dynamo is illustrated in FIG. 5. Astator 14 has 6 poles with armature coils 15a, 15b and 150' wound onevery other pole. Voltages generated at the armature coils 15d, 15b and15c are respectively stored in discharge capacitors 3a, 3b and 3cthrough diodes 2a, 2b and 20. A rotor 17 has a transmuted 2- poleconstruction in which a 2-pole rod magnet 12' and magnetic cores 13'disposed on the poles are supported on a non-magnetic material, with abalance weight 16 arranged on the opposite side. The magnetic poles ofthe rotor 17 are, like those of the stator 14, arranged at an angle of60. '(This is due to the 6 poles possessed by the stator 14.) Now, letthe number of turns of the armature coils be N inductance L, averagecurrent in the coils l and magnetic flux per pole d: in the conventionaldevice, and'the number of turns of the armature coils N, inductance L',average current in the coils I and magnetic flux per pole for the deviceaccording to the invention. In order for the charging voltage of thecapacitor of the device according to the invention to be the same asthat of the conventional device, it suffices if the number of turns ofeach of the armature coils 15a, 15b and 15c is the same as the totalnumber of turns of the series armature coils 15a, 15b, 15f, provided themagnetic flux d1 is'equal for both devices. The armature coils of theconventional device goes through a 3-cycle power-generating action forevery revolution of the rotor, while, in the device according to theinvention whose rotor has 2 poles, each of the armature coils 15a, 15band 15c performs only one cycle of power generation for each turn of therotor 17. This results in value of current I one third as small as thecurrent I produced in the case of the conventional device, and thereforeit suffices to provide a coil with a section one third as small as thatof the conventional device, the heating effect due to the current beingthe same, making it possible to have the number of the winding turnsthree times more than that in the case of the conventional device withthe same winding space. Further, since windings are provided on everyother pole in the device according to the invention instead of on all ofthe six poles as in the conventional device, twice as much winding spaceis available per pole as in the case of the conventional device. In all,six times as many windings as in the case of the conventional device canbe provided on every other pole of the stator 14, with the result thatthe number of turns N which is equal to the total number of turns 6N ofthe conventional device can be realized in one armature coil. As regardsthe inductance of each coil, the inductance of all the coils which areconnected in series in the case of the conventional device is 6L. Bycontrast, the number of turns of an armature coil per pole is six timesas large in the device of the invention, and since the inductance isproportional to the square of the number of turns, the inductance perpole of the device according to the invention is 6 L 36L. From this itwill be understood that the series inductance involved in the chargingof the capacitor is six times as high as in the conventional device(36L/6L 6). When the. engine is at low speed,

the frequency of the voltage produced is low and therefore the voltagedrop due to the inductance inserted in series for charging the capacitoris negligible, but at high velocity the frequency of the voltagegenerated is high resulting in a larger voltage drop due to theinductance. According to the invention, therefore, the voltage drop dueto the inductance prevents overvoltage of the capacitor-charging voltageat high speed, making it possible to obtain a stable characteristic ofthe capacitor-charging voltage as shown by the solid line a of FIG. 3.Further, the reduction of the magnet to one third of the one usedin theconventional device results in a lower magnet cost, whereas thereduction of iron loss of the stator core to one third of that in theconventional device causes less heat to be generated.

The electrical circuit of the device according'to the invention will beexplained below in detail mainly with reference to FIG. 5. The armaturecoils 15a, 15b and 15c the construction of which is described above areconnected in series with the diodes 2a, 2b and 2c, capacitors 3a, 3b and3c, and ignition coils 5a, 5b and 5c respectively, thereby forming anignition circuit.

The secondary terminals of the ignition coils are con-- nected withignition plugs 6a, 6b and 6c of the cylinders respectively, while theterminals A, B and C which are connected with diodes 2a, 2b and 2c andcapacitors 3a, 3b and 3c are also connected in parallel with an SCR4through the diodes 9a, 9b and 90. When the SCR4 is made to conduct byignition timing signals from the ignition timing dynamo, charges storedin the capacitors 3a, 3 b and 3c are discharged through the ignitioncoils 5a, 5b and 5c respectively. The output of the timing dynamo 10 issuch that the ignition timing signals are produced three times for everyturn of the crank shaft. The magnetic fluxes 4; in the armature coils15a, 15b and 15c undergo changes as shown in FIGS. 7(a), 7(b) and 7(c)respectively with regard to the rotational angle 9 of the rotor 17 ofthe magnet dynamo 1. Let the period of one cycle of the rotor 17 to T,and then from the fact that the rotor has two poles, it follows that themagnetic fluxes in the armature coils'are periodically produced at everyl/3T of the interval. The result is the generation-in the armature coils15a, 15b and 15c of voltages E, as shown in FIGS. 8(a), 8(b) and 8(c)respectively, inwhich each of the reverse voltages is one half of eachof the capacitor-charging voltages Eco,

with a voltage cycle being produced in each coil. Now, assuming that thetiming signals as shown in FIG. 9 are applied to the gate of the SCR4 atpoints of voltage variations as indicated in FIGS. 8(a), 8(b) and 8(c),the

voltage generated at the armature coil 15a (FIG. 8(a)) is charged in thecapacitor 3a. The charges stored at the capacitor 3a are dischargedthrough the diode 9a, SCR4 and ignition coil 50 at point a of FIG. 9where the SCR4 begins conducting. The resultant discharging current inthe capacitor 3a generates a high voltage at the secondary of theignition coil 5a, thereby making ignition sparks obtainable at theignition plug 6a. Then a voltage as shown in FIG. 8(b) is produced atthe armature coil l5b' and charged to the capacitor 3b in the samemanner as in the case of capacitor 3aSCR4 conducts and the capacitor 3bis discharged, thereby generating a high voltage at the secondary of theignition coil 5b to produce ignition sparks at the ignition plug 6b. Inlike manner, ignition sparks can be obtained at the ignition plug 60 atpoint c of FIG. 9 by means of the armature coil 150'.

It will be seen from the above description that the voltage generated atthe armature coil 15a is charged to the capacitor 30 correspondingthereto, and the charges in the capacitor 3a are discharged through thecorresponding ignition coil 5a at point a of FIG. 9 when the othercapacitors 3b and 3c are uncharged. For this reason, no high voltage isgenerated at the secondary of the coils 5b and 5c at point a of FIG. 9,completely eliminating the trouble of erroneous ignition. The same istrue for ignition points b and c of FIG. 9, at which ignition sparkscompletely free from erroneous ignition are supplied to the ignitionplugs 6b and 6c respectively. Also, since the reverse voltage generatedat an armature coil and which does not act to charge the capacitor isone half as low, it is possible to reduce the breakdown voltage in thereverse direction of the diodes 2a, 2b and 2c. Another feature of theinvention is that, in the case of reverse rotation which sometimesoccurs in a 2-cycle engine, voltages generated in the armature coil arein opposite polar states with respect to the polarity of the voltagesshown in FIG. 8. When considering the armature coil 15c specifically,reverse rotation of the rotor (in the direction opposite to thatindicated by arrow causes the capacitor 3c to be charged at a voltagewhich is one half the capacitor voltage for the forward rotation.However, since a timing signal is applied to the SCR4 at point b of FIG.9 to energize the SCR4, the charges stored in the capacitor 3c at thatpoint pass a discharging current in the ignition coil c, therebygenerating a high voltage in the ignition plug 6c. This voltage is aboutone half of that produced in the forward rotation, and therefore lesscapable of firing the fuel. In addition, the firing position involved isthe one where ignition sparks are produced at the ignition plug 6b inthe forward rotation, and therefore the piston of the cylinder of theignition plug 6c is at the bottom dead center, with the result that evenif the fuel is successfully ignited, the piston is unable to developaturning effort large enough to maintain the reverse rotation of theengine. The same is true for the armature coils b and 15a, therebycompletely preventing the reverse rotation of the 2-cycle engine.

An electrical circuit of another embodiment is shown in FIG. 6a, inwhich the component elements are rearranged without affecting theoperation at all. This embodiment is also applicable to a 6-cylinderengine if a double ignition coil circuit which generates ignition sparkssimultaneously at two ignition plugs is formed as shown in FIG. 6b byconnecting an ignition plug to both terminals of the secondary windingof each ignition coil.

The above-described embodiment shows an ignition device mounted on a2-cycle 3-cylinder engine. However, unless the double ignition coilcircuit of FIG. 6b is employed, this invention is primarily intended toemploy a magnet dynamo 1 including a combination of a 2-pole rotor and2n-pole stator in the case of a 2-cyc1e engine with n cylinders, and amagnet dynamo l including a combination of a 2 -po1e rotor and a statorwith at least n poles or 2n poles in the case of a 4-cycle engine withan even or odd number of cylinders respectively (n: the number ofcylinders). Especially, in the case where the discharge capacitors 3a,3b and 3c are charged in steps, the number of stator poles is furtherincreased by the number of times equal to that of the steps and armaturecoils are wound on every other pole.

I claim:

1. In a magneto-dynamo-operated ignition device for a multi-cylinderengine, in which a magneto dynamo is employed as a power supply; aplurality of discharge capacitors charged thereby equal to at least thenumber of cylinders, secondary windings of a plurality of ignition coilsequal to at least one half the number of cylinders producing highignition voltages by discharging said capacitors associated with eachcoil; comprising: the magneto dynamo having a 2-pole rotor and a statorwith poles of even number determined in accordance with the number ofcylinders, and armature coils wound on every other stator pole, aplurality of discharging circuits of said discharge capacitors beingselectively energized through a common rectifier with a controlelectrode which is controlled by an ignition timing signal from theignition timing dynamo produced for eachcylinder as said rotor engagesmagnetically with each armature coil.

2. A magneto-dynamo-operated ignition device for multi-cylinder enginecomprising:

a magneto dynamo having a plurality of charging coils adapted to producea plurality of output voltages successively for every one rotationthereof;

a plurality of charging circuits connected to said plurality of chargingcoils respectively, each of said charging circuits including, acapacitor for storing electric charges supplied from the correspondingone of said output voltages of said charging coils;

discharging means comprising a plurality of discharging circuitscorresponding to said plurality of charging circuits respectively;

a switching means connected commonly to said plurality of dischargingcircuits, each of said discharging circuits including, ignition coilmeans for delivering an ignition voltage to a plug connected thereto andbeing connected to said capacitor of the corresponding charging circuitfor discharging the stored electric charges of said capacitor throughand means for closing said switch element periodically in synchronismwith the rotation of the engine.

3. The magneto-dynamo-operated ignition device of claim 2 wherein saidmagneto dynamo comprises:

a stator having a plurality of substantially equally spaced poles whosenumber is two times a number of cylinders of the engine and armaturecoils wound on alternate ones of said poles, and rotor having two polesdisposed thereon with a space substantially equal to that between twoadjacent ones of said poles of said stator, said armature coilsproducing output voltages successively in accordance with the rotationof said rotor.

4. The magneto-dynamo-operated ignition device of claim 2 wherein saidplurality of charging circuits correspond to said armature coils,respectively, each of said charging circuits further including a firstdiode connected through said capacitor associated therewith to thecorresponding one of said armature coils for charging said capacitorwith electric charges, when said corresponding armature coil producessaid output voltage.

5. The magneto-dynamo-operated ignition device of claim 2 wherein saiddischarging means further includes: a second diode and said ignitioncoil means including primary and secondary coils, said primary coilbeing connected through said second diode to said capacitor of thecorresponding charging circuit, for

discharging said electric charges charged in said capacitortherethrough; thereby producing a high ignition voltage at saidsecondary coil when said switching means is closed, said secondary coilbeing connected to two plugs mounted on a 6. The magneto-dynamo-operatedignition device of claim 2 wherein said means for closing said switchelement comprises: an ignition timing generator for producing signalssuccessively; each at a predetermined time relating to the desiredignition timing of said cylinders after said capacity of any one of saidcharging circuits has been charged, said signals being applied to saidswitching means thereby closing the same periodically.

7. The magneto-dynamo-operated ignition device of claim 2 wherein saidengine has an even number of cylinders and said magneto dynamocomprises: a stator having a plurality of substantially equally spacedpoles whose number is equal to the even number of said cylinders,armature coils wound on alternate ones of said poles, and a rotor havingtwo poles disposed thereon with a space substantially equal to thatbetween two adjacent ones of said poles of said stator, said armaturecoils producing output voltages successively in accordance with therotation of said rotor.

1. In a magneto-dynamo-operated ignition device for a multicylinderengine, in which a magneto dynamo is employed as a power supply; aplurality of discharge capacitors charged thereby equal to at least thenumber of cylinders, secondary windings of a plurality of ignition coilsequal to at least one half the number of cylinders producing highignition voltages by discharging said capacitors associated with eachcoil; comprising: the magneto dynamo having a 2-pole rotor and a statorwith poles of even number determined in accordance with the number ofcylinders, and armature coils wound on every other stator pole, aplurality of discharging circuits of said discharge capacitors beingselectively energized through a common rectifier with a controlelectrode which is controlled by an ignition timing signal from theignition timing dynamo produced for each cylinder as said rotor engagesmagnetically with each armature coil.
 2. A magneto-dynamo-operatedignition device for multi-cylinder engine comprising: a magneto dynamohaving a plurality of charging coils adapted to produce a plurality ofoutput voltages successively for every one rotation thereof; a pluralityof charging circuits connected to said plurality of charging coilsrespectively, each of said charging circuits including, a capacitor forstoring electric charges supplied from the corresponding one of saidoutput voltages of said charging coils; discharging means comprising aplurality of discharging circuits corresponding to said plurality ofcharging circuits respectively; a switching means connected commonly tosaid plurality of discharging circuits, each of said dischargingcircuits including, ignition coil means for delivering an ignitionvoltage to a plug connected thereto and being connected to saidcapacitor of the corresponding charging circuit for discharging thestored electric charges of said capacitor through and means for closingsaid switch element periodically in synchronism with the rotation of theengine.
 3. The magneto-dynamo-operated ignition device of claim 2wherein said magneto dynamo comprises: a stator having a plurality ofsubstantially equally spaced poles whose number is two times a number ofcylinders of the engine and armature coils wound on alternate ones ofsaid poles, and a rotor having two poles disposed thereon with a spacesubstantially equal to that between two adjacent ones of said poles ofsaid stator, said armature coils producing output voltages successivelyin accordance with the rotation of said rotor.
 4. Themagneto-dynamo-operated ignition device of claim 2 wherein saidplurality of charging circuits correspond to said armature coils,respectively, each of said charging circuits further including a firstdiode connected through said capacitor associated therewith to thecorresponding one of said armature coils for charging said capacitorwith electric charges, when said corresponding armature coil producessaid output voltage.
 5. The magneto-dynamo-operated ignition device ofclaim 2 wherein said discharging means further includes: a second diodeand said ignition coil means including primary and secondary coils, saidprimary coil being connected through said second diode to said capacitorof the corresponding charging circuit, for discharging said Electriccharges charged in said capacitor therethrough; thereby producing a highignition voltage at said secondary coil when said switching means isclosed, said secondary coil being connected to two plugs mounted on a 6.The magneto-dynamo-operated ignition device of claim 2 wherein saidmeans for closing said switch element comprises: an ignition timinggenerator for producing signals successively; each at a predeterminedtime relating to the desired ignition timing of said cylinders aftersaid capacity of any one of said charging circuits has been charged,said signals being applied to said switching means thereby closing thesame periodically.
 7. The magneto-dynamo-operated ignition device ofclaim 2 wherein said engine has an even number of cylinders and saidmagneto dynamo comprises: a stator having a plurality of substantiallyequally spaced poles whose number is equal to the even number of saidcylinders, armature coils wound on alternate ones of said poles, and arotor having two poles disposed thereon with a space substantially equalto that between two adjacent ones of said poles of said stator, saidarmature coils producing output voltages successively in accordance withthe rotation of said rotor.